1. Cross-Reference to Related Patent
U.S. Pat. No. 4,875,644, issued Oct. 24, 1989, entitled xe2x80x9cElectro-Repulsive Separation System for De-Icing,xe2x80x9d by Lowell J. Adams, et al., the disclosure of which is incorporated herein by reference (hereinafter referred to as the xe2x80x9cElectro-Repulsive Separation System Patentxe2x80x9d).
2. Field of the Invention
The invention relates to de-icers for aircraft and, more particularly, to de-icers that operate by deforming ice-accumulating surfaces.
The invention relates to planar coils and, more particularly, to planar coils especially adapted for use in a force-producing device such as a de-icer.
3. Description of the Prior Art
The accumulation of ice on aircraft wings and other structural members in flight is a danger that is well known. As used herein, the term xe2x80x9cstructural membersxe2x80x9d is intended to refer to any aircraft surface susceptible to icing during flight, including wings, stabilizers, engine inlets, rotors, and so forth. Attempts have been made since the earliest days of flight to overcome the problem of ice accumulation. While a variety of techniques have been proposed for removing ice from aircraft during flight, these techniques have had various drawbacks that have stimulated continued research activities.
One approach that has been used extensively is so-called mechanical de-icing. In mechanical de-icing, the leading edges of structural members are distorted in some manner so as to crack ice that has accumulated thereon for dispersal into the airstream. A popular mechanical de-icing technique is the use of expandable tube-like structures that are periodically inflatable. Inflation of the structures results in their expansion or stretching by 40% or more. Such expansion typically occurs over approximately 2-6 seconds and results in a substantial change in the profile of the de-icer, thereby cracking accumulated ice. Unfortunately, expansion of the devices can negatively influence the airflow passing over the aircraft structure. Also, they are most effective when ice has accumulated to a substantial extent, approximately 0.25 inch or more, thereby limiting their effectiveness. Desirably, ice removal would be accomplished long before accumulations approximating 0.25 inch have been attained.
A more recent mechanical de-icing technique utilizes internal xe2x80x9chammersxe2x80x9d to distort the leading edges of structural members. Such an approach is exemplified by U.S. Pat. No. 3,549,964 to Levin et al., wherein electrical pulses from a pulse generator are routed to a coil of a spark-gap pressure transducer disposed adjacent the inner wall of the structural member. The primary current in the coil induces a current in the wall of the structural member and the magnetic fields produced by the currents interact so as to deform the member.
U.S. Pat. Nos. 3,672,610 and 3,779,488 to Levin et al. and U.S. Pat. No. 4,399,967 to Sandorff disclose aircraft de-icers that utilize energized induction coils to vibrate or torque the surface on which ice forms. Each of these devices employs electromagnetic coils or magneto-restrictive vibrators located on the side of the surface opposite to that on which ice accumulates. In U.S. Pat. No. 3,809,341 to Levin et al., flat buses are arranged opposite one another, with one side of each bus being disposed adjacent an inner surface of an ice-collecting wall. An electric current is passed through each bus and the resulting interacting magnetic fields force the buses apart and deform the ice-collecting walls.
A more recent approach is shown by U.S. Pat. No. 4,690,353 to Haslim et al. In the ""353 patent, one or more overlapped flexible ribbon conductors are imbedded in an elastomeric material that is affixed to the outer surface of a structural member. The conductors are fed large current pulses from a power storage unit. The resulting interacting magnetic fields produce an electro-expulsive force that distends the elastomeric member. The distension is almost instantaneous when a current pulse reaches the conductors, and is believed to be effective in removing thin layers of ice. Although the device disclosed in the ""353 patent is believed to be an improvement over previous mechanical de-icing techniques, certain drawbacks remain. One of the drawbacks relates to the direction of current flow in adjacent electrically conductive members. It is believed that the current flow disclosed in the ""353 patent produces inefficiencies that significantly restrict the effectiveness of the device.
The Electro-Repulsive Separation System Patent disclose a device that is an improvement over that disclosed in the ""353 patent. In the Electro-Repulsive Separation System Patent, the electrically conductive members are arranged such that a greater electro-expulsive force can be generated than with the serpentine configuration disclosed in the ""353 patent. Also, the Electro-Repulsive Separation System Patent teaches the delivery of a current pulse of predetermined magnitude, shape and duration that provides more effective de-icing action.
Despite the advances taught by the prior art, particularly the Electro-Repulsive Separation System Patent, there remains a need for a de-icer that provides effective de-icing action. In particular, it is desired to have a de-icer that has the force-generating capabilities of various prior mechanical de-icers without the drawbacks associated therewith, such as large size, difficulty in retrofitting existing structural members, and other problems.
The accumulation of ice on aircraft wings and other structural members in flight is a danger that is well known. As used herein, the term xe2x80x9cstructural membersxe2x80x9d is intended to refer to any aircraft surface susceptible to icing during flight, including wings, stabilizers, engine inlets, rotors, and so forth. Attempts have been made since the earliest days of flight to overcome the problem of ice accumulation. While a variety of techniques have been proposed for removing ice from aircraft during flight, these techniques have had various drawbacks that have stimulated continued research activities.
One approach that has been used extensively is so-called mechanical de-icing. In mechanical de-icing, the leading edges of structural members are distorted in some manner so as to crack ice that has accumulated thereon for dispersal into the airstream. A popular mechanical de-icing technique is the use of expandable tube-like structures that are periodically inflatable. Inflation of the structures results in their expansion or stretching by 40% or more. Such expansion typically occurs over approximately 2-6 seconds and results in a substantial change in the profile of the de-icer, thereby cracking accumulated ice. Unfortunately, expansion of the devices can negatively influence the airflow passing over the aircraft structure. Also, they are most effective when ice has accumulated to a substantial extent, approximately 0.25 inch or more, thereby limiting their effectiveness. Desirably, ice removal would be accomplished long before accumulations approximately 0.25 inch have been attained.
A more recent mechanical de-icing technique utilizes internal xe2x80x9chammersxe2x80x9d to distort the leading edges of structural members. Such an approach is exemplified by U.S. Pat. No. 3,549,964 to Levin et al., wherein electrical pulses from a pulse generator are routed to a coil of a spark-gap pressure transducer disposed adjacent the inner wall of the structural member. The primary current in the coil induces a current in the wall of the structural member and the magnetic fields produced by the currents interact so as to deform the member.
U.S. Pat. Nos. 3,672,610 and 3,779,488 to Levin et al. and U.S. Pat. No. 4,399,967 to Sandorff disclose aircraft de-icers that utilize energized induction coils to vibrate or torque the surface on which ice forms. Each of these devices employs electromagnetic coils or magneto-restrictive vibrators located on the side on the surface opposite to that on which ice accumulates. In U.S. Pat. No. 3,809,341 to Levin et al., flat buses are arranged opposite one another, with one side of each bus being disposed adjacent an inner surface of an ice-collecting wall. An electric current is passed through each bus and the resulting interacting magnetic fields force the buses apart and deform the ice-collecting walls.
A more recent approach is shown by U.S. Pat. No. 4,690,353 to Haslim et al. In the ""353 patent, one or more overlapped flexible ribbon conductors are imbedded in an elastomeric material that is affixed to the outer surface of a structural member. The conductors are fed large current pulses from a power storage unit. The resulting interacting magnetic fields produce an electro-expulsive force that distends the elastomeric member. The distension is almost instantaneous when a current pulse reaches the conductors, and is believed to be effective in removing thin layers of ice. Although the device disclosed in the ""353 patent is believed to be an improvement over previous mechanical de-icing techniques, certain drawbacks remain. One of the drawbacks relates to the direction of current flow in adjacent electrically conductive members. It is believed that the current flow disclosed in the ""353 patent produces inefficiencies that significantly restrict the effectiveness of the device.
The Electro-Repulsive Separation System Patent discloses a device that is an improvement over that disclosed in the ""353 patent. In the Electro-Repulsive Separation System Patent, the electrically conductive members are arranged with current flow in a common direction in a conductor layer such that a greater electro-expulsive force can be generated than with the serpentine configuration disclosed in the ""353 patent. Also, the Electro-Repulsive Separation System Patent teaches the deliver of a current pulse of predetermined magnitude, shape and duration that provides more effective de-icing action.
Despite the advances taught by the prior art, particularly the Electro-Repulsive Separation System Patent, there remains a need for a de-icer that provides effective de-icing action. A particular concern relates to the electrically conductive members that are used with the prior devices. It is desired to provide coils that are as thin as possible, while being relatively inexpensive and easy to manufacture. Desirably, any such coils would have a very high efficiency, that is, they would generate more force than prior electrically conductive members for a given current input. The coils also desirably would permit a small or large area of force production as desired for a de-icer construction.
The present invention overcomes the foregoing drawbacks of the prior art and provides a new and improved de-icer especially adapted for attachment to external surfaces of structural members. In one embodiment of the present invention, an inductor coil is positioned in proximity with the outer surface of a structural member. The coil has a first side that is disposed in contact with the surface and a second side that is spaced from the surface. The coil is movable away from and toward the surface. A support member is provided for the coil, the support member being flexible in order to permit the coil to move relative to the surface. A portion of the support member defines an ice-accumulating surface that moves in response to movement of the coil. Preferably, the coil and support member are provided in an integral construction that can be bonded or otherwise attached to the leading edge of the structural member without modifying the structural member.
An alternative embodiment of the invention calls for providing a metal target that is disposed intermediate the coil and the support member. Another alternative embodiment calls for disposing the target intermediate the coil and the structural member. Yet an additional alternative embodiment calls for providing a target (doubler) that is attached to the inner surface of the structural member.
With each embodiment of the invention, the support member is rapidly, and forcefully, displaced away from the structural member upon passing a short-duration, high-current pulse through the coil. If the structural member is metal, the structural member functions as a target and the coil is displaced away from the surface; if the structural member is non-metal (such as a composite material), and if a surface-contacting target is not used, the coil remains positioned against the surface. The current flows creates an electromagnetic field that induces eddy currents in the target, structural member (if metal), and support member (if metal). Upon collapse of the electromagnetic field in the coil, the support member is pulled rapidly to its rest position.
In contrast with prior mechanical de-icers, the de-icer according to the invention is exceedingly effective, while avoiding many of the drawbacks of the prior art. Most of the forces that are applied to the structural member are compressive forces that are more easily accommodated than tensile forces that are produced by various other mechanical de-icers. Further, the device can be fitted readily to structural members, either as part of new construction or as a retrofit.
Because the device operates on an eddy current principle, it completely avoids problems arising from directional current flow, and it provides a more effective ice-shedding action than has been possible with previous devices. In part, the effectiveness of the device is enhanced because the ice-accumulating surface is displaced a relatively great distance at a high rate of acceleration. Although the displacement is not enough to negatively affect the airflow passing over the structural member, the displacement is more than 20 times greater than the displacement that occurs with such devices as are disclosed in prior eddy current-type de-icers. The device also produces about 20% greater eddy current induction than prior internally disposed eddy current de-icers because the coil and the target are in surface-to-surface contact with each other, or nearly so. The referenced internally disposed de-icers require a substantial gap between the coil and the target are in surface-to-surface contact with each other, or nearly so. The referenced internally disposed de-icers require a substantial gap between the coil and the structural member in order to prevent possible damage to the coil upon rebounding of the structural member. The efficiency of the present invention also is great because the ice-accumulating surface that is displaced is relatively thin and is resiliently mounted to the structural member. In those de-icers that distort the structural member itself, the ice-accumulating surface is relatively thick and may be relatively difficult to distort.
The foregoing and other features and advantages of the present invention will become more apparent when viewed in light of the description of the best embodiment of the invention and the drawings that follow, which together form a part of the specification.
The present invention addresses the foregoing concerns and provides a new and improved planar coil construction especially adapted for use as part of a de-icer. The planar coil according to the invention includes a first sheet-like member defined by a first, continuous, electrical conductor having a plurality of turns and first and second ends. The first end of the first conductor defines an electrical input to the coil, and the second end of the first conductor defines an electrical output. The invention includes a second sheet-like member defined by a second, continuous, electrical conductor having a plurality of turns and first and second ends. The first end of the second conductor defines an electrical input, and the second end of the second conductor defines an electrical output from the coil. The second end of the first conductor and the first end of the second conductor are electrically connected. The first and second sheet-like members are disposed parallel to each other with the turns of the first and second conductors being positioned adjacent each other. The direction of current flow through the turns of the first conductor can be arranged to be substantially the same as that through the turns of the second conductor, or it can be arranged to be substantially opposite that through the turns of the second conductor. In addition, within a sheet-like member the adjacent conductors from the center out have current flow in the same direction, which is of particular importance for electro-repulsive force de-icers.
In one embodiment of the invention, the turns are rectangular, while in other embodiments the turns are spiral-shaped, square, or any other desired geometry. The invention also includes a technique for separating the sheet-like members by a dielectric layer, as well as a means for encapsulating the sheet-like members. Additional sheet-like members can be provided, if desired, and connected to each other and to the first and second sheet-like members. When more than two members are used, if the direction of current flow in a given layer is opposite to the direction of current flow in adjacent layers, a strong repulsive force is created when a high current pulse is applied. If the direction of current flow in a given layer is in the same direction as in adjacent layers, it may be used for an eddy current de-icer. The invention also contemplates incorporating a ferromagnetic or paramagnetic material (hereinafter referred to as xe2x80x9cmagnetic materialxe2x80x9d) on the outer and/or inner surface of the coil in order to improve or shape the magnetic field generated by the coil and increase the resultant force.
Regardless of the embodiment of the invention that is utilized, the sheet-like members can be manufactured readily from metal foil or a flat-braided conductor. The coil according to the invention can be assembled readily, and it provides significant force-generating capabilities compared with prior coil constructions.
The foregoing and other features and advantages of the present invention will become more apparent when viewed in light of the description of the best embodiment of the invention and the drawings that follow, which together form a part of the specification.